1. Field of the Invention
The present invention relates generally to an information optical reader which optically reads an information code such as a Quick Response (QR) code (registered trademark) directly marked on an object such as a commercial article or the like by a printing work, an attaching work or a marking press, and more particularly to the information optical reader which optically reads an information code embossed, engraved or carved on an object by the marking press so as to form concavities and/or convexities on the object.
2. Description of Related Art
To record information about an object such as a commercial article in the object, an information code has been directly marked on the object by printing or marking press. When the direct marking such as dot impact direct marking or laser marking is performed for the object to form an information code carved on the object, grooves or concavities are formed on an information marking area of the object. To read the information code carved on the object, the marking area of the object is illuminated with an information optical reader, and the reader analyzes an intensity distribution of light reflected on the object. However, when the marking area of the object is illuminated from a position just above the marked area, the reflected light sometimes has a uniform distribution of intensity due to a uniform reflectance of the light on the marking area. In this case, the reader cannot read the information code from the object.
To solve this problem, a user illuminates the marked area of the object with a handy type information optical reader while adjusting the lighting position and direction of the reader to the object so as to illuminate the marked area from an appropriate direction slanting to the object. Further, in case of a stationary information optical reader, the user repeatedly changes an illuminator of the reader to another one while checking clearness of the read information code, and the user finally finds an illuminator optimum to the information code and the object.
As one of stationary optical readers, Published Japanese Patent First Publication No. 2005-18391 has disclosed a code reader. In this reader, a user repeatedly changes an illumination color of light set in the reader to check a difference in brightness of the color between light reflected from a code carved on an object and light reflected from a background area. The user finally finds out an illumination color optimum to the code according to the brightness difference.
Further, as another stationary optical reader, Published Japanese Patent First Publication No. 2000-99625 has disclosed a letter recognizer. In this recognizer, a code carved on a wafer is illuminated with each of a light source of a bright field illumination system and a light source of a dark field illumination system to detect a bright field image and a dark field image, and the code is recognized based on a difference between the images. Further, a position of the light source of the dark field illumination system is manually changed to maximize a contrast in the dark field image.
In case of the code reader disclosed in the Publication No. 2005-18391, illumination colors such as red, blue and green are selected one by one to read a code illuminated with light of each selected color. However, because only the bright field illumination is used, a mirror reflection easily occurs on the surface of the object. Therefore, it is difficult to read a code directly marked on the object in the bright field illumination.
Further, in case of the letter recognizer disclosed in the Publication No. 2000-99625, the light sources of the bright and dark field illumination systems and the position of the light source of the dark field illumination system are manually changed. However, this change is performed without considering the color, the material or the shape of the object. Further, it is required to repeatedly change the light sources of the bright and dark field illumination systems and the position of the light source of the dark field illumination system until an image with a high contrast is found out by chance.
Further, when a light is incident on a glossy or glazed paper at a large incident angle to the paper to read an information code printed on the paper, a mirror reflection often occurs on the surface of the paper. In this case, a portion of a code image corresponding to a mirror reflection portion of the code is always set at a bright (or white) level regardless of a black or white color of the mirror reflection portion. Therefore, the code cannot be correctly read. Particularly, when an information code is carved on a glossy metallic plate by means of the direct marking, a mirror reflection considerably occurs on the surface of the plate. Therefore, a conventional information optical reader cannot-correctly read an information code printed or carved on a glossy or glazed object.